makc wrote:Chris Peterson wrote:The guy in the space ship could tell without uncertainty that he is in a non-inertial frame
how? if his ship accelerates with, say, 1g, he wouldnt think his frame is very different from the one we have on earth.
It is certainly true that you can construct a test that makes it very difficult to determine the actual conditions. That isn't really the point of the Twin Paradox as a thought experiment, of course. If you choose to do that, however, it simply means that the twins who are now lacking accurate knowledge of their frames will be unable to predict in advance what will happen. They can still complete the experiment, see the actual result, and conclude the range of possible conditions that led to that result- the simplest being that the younger twin was in a non-inertial frame part of the time, while the older was not.
let's take a look at similar situation, again, suppose the whole universe is one spinning earth, how do you know it is actually spinning? you have pendulums changeing their planes, but those can be explained by Coriolis force. how do you know if this force is real or not? same way, the guy in ship has his swiss watch that his father gave him, and this watch had never let him down. now Chris calls and say, you know what your whatch display completely bogus and unscientific data. What? Come on, he trusts his watch. And he knows he's completely stationary relative to the floor he stands on, etc.
Again, you can assume a malicious experimenter, constructing ambiguous cases. If you observe effects that are consistent with a Coriolis effect, it is reasonable to assume you are in a rotating frame- that's what produces the Coriolis effect. Yes, there may be other causes, in which case you would have to construct different tests. When you start talking about rotation of the entire Universe, however, you get into muddy water. You're stepping close to the notoriously tricky
Mach's Principle, as well as issues about just what rotation of the Universe even means.
The problem is that the twin doesn't observe rapid aging. He's in a non-inertial frame, and observations outside that frame are distorted.
Oh right, he does not observe, he is watching his porn collection instead. He does, Chris, no matter how much you hate his frame, but this is perfectly valid (although non-inertial) frame. In fact, most of frames in the Universe are more like his one.
The point is that his observation is distorted. That is always the case when making an observation between non-inertial frames (a condition under which SR fails). In actual practice, astronomers make compensations all the time for observations made between different frames.
when they are both in inertial frames.
they are never both in inertial frames.
Actually, the twin who stays behind is in an inertial frame the entire time. That's a given in the thought experiment, which (quite properly) ignores things like the gravity of the Earth, or planetary motion.
